In the following the word robot will be used instead of robot manipulator. Typically the robot is an industrial robot for automated production applications.
Typical industrial task applications where robots are used are welding, cutting, painting, gluing, material handling, and material removing, etc. A robot performs a repetitive sequence of movement along a predefined path. Considering the high number of task runs within a specific time span, for instance one year, it is very important to reduce the cycle time. Providing the minimum cycle time for a specific robot task is therefore an essential step in robot applications on the factory floor. Reduction of the cycle time a few percent will increase the productivity in a production line considerably.
It is of general interest to let a robot perform the path motion as fast as possible. Minimizing motion time can significantly shorten cycle times and improve machine utilization, and thus make automation affordable in applications for which throughput and cost effectiveness is of major concern.
Reduction of motion time can be achieved through optimization in different robotics areas such as general robot design methodology, kinematics, dynamics, structure or arm shape, robot controller, time optimal controls, task-based design, and robot cell design or robot optimal placement. For a given robot, cycle time depends on many parameters, such as the position of the robot relative to the task, the sequence in which the points are visited, the maximum velocities and accelerations of the actuators, the relative position of the points, or the configuration of the arm along the track.
The performance of a robot during the achievement/execution of a task depends on the relative position of the robot and the task. Thus, a robot ill placed at its workstation, takes the risk of an inefficient operation, even as to fall in singularities.
A robot cell is an essential element for automated production and may consist of one or several industrial robots, one or a number of work objects on which the robot would perform tasks, and other cell equipments. For a robot cell containing multiple robots, robots can work either independently or collectively. By robots working collectively it is meant, for example, that one a robot holds a work object while another robot perform tasks on the work object.
A coordinate system, normally referred to as the “world coordinate system”, is used to define and manage relative locations of robots, work objects, and other cell equipments in a robot cell. In practice, coordinate systems fixed on robots, normally referred to as “robot coordinate systems”, are defined to specify locations of robots in the world coordinate system. Coordinate systems fixed on work objects, normally referred to as “object coordinate systems”, are defined to specify locations of work objects in either a user coordinate system, or a robot coordinate system or in the world coordinate system. Examples of different coordinate systems used to define a robot cell are shown in FIGS. 1 and 2.